Spatial and Temporal Distribution of Drought and Flood in Loess Plateau in Different Hydrological Years

Changes of global climate will lead to more uncertainty of annual precipitations in Loess Plateau, which is a critical factor for causing droughts or floods in that area． In order to design better strategy to manage water resource in different hydrological years, special and temporal distribution of drought and flood in Loess Plateau was analyzed． Precipitation data from 263 meteorological stations were used to identify typical hydrological years, including wet year, normal year and dry year． Then Standardized Precipitation Index（SPI）was calculated as an indicator for droughts and floods． Results showed that droughts occurred in all kinds of hydrological years． In wet year, drought area, flood area took up 5.7% and 40.9%, respectively． In normal year, drought area and flood area accounted for 12.7% and 19.3%, respectively． However, drought area took up 44.4% and flood area took up 17.9% in dry year． Spatial distribution of droughts in wet year, normal year and dry year was obviously different． Spring was usually dry in all kinds of hydrological years． Drought area in spring would decrease after beginning of rainy season in wet year and normal year, however rainfall in rainy season of dry year could not alleviate spring drought effectively． What’s more, autumn in dry year was wet． According to results, drought and flood were frequent in Loess Plateau, allocation of water conservancy facilities and field irrigation facilities in Loess Plateau were critical for agriculture and ecosystem in Loess Plateau．